Feed finger for automatic screw machines and gripping element therefor



Jan. 6, 1953 F. L. GREEN 2,6 4,102

FEED FINGER FOR AUTOMATIC SCREW MACHINES AND GRIPPING ELEMENT THEREFORFiled June 29, 1950 2 SHEETS-SHEET 1 26 Frank Green & mm2$ Jan. 6, 1953REW MACHINES REFOR 2 SHEETSSHEET 2 F. GREEN 2,624,102 FEED FIN FOR TOTIC AND IPPI EL T Filed June 29, 1950 19' V A -m' iiNvxsm-ravmaniL-Gl/eem.

@Wj" )LM-v- /CU Patented Jan. 6, 1 953 AUTOMATIC SCREW GRIPPING ELEMENTFEED FINGER FOR MACHINES AND THEREFOR Frank L. Green, Rockton, 111.Application June 29, 1950, Serial No. 171,061

8 Claims.

This invention relates to a so-called feed finger mountable on thereciprocable feed head of an 1 gripping pressure applied to the barbeing derived by axial compression of a body of yieldable materialwithin the finger.

One object is to provide a feed finger in which the means for adjustingthe gripping pressure on the work bar is located at the forward oroutboard end of the feed finger so as to permit the gripping pressure tobe adjusted without removing the finger from its mounting in the screwmachine.

A more detailed object is to provide a feed finger of the abovecharacter in which the gripping pressure is adjusted by a plug'threadinginto the forward end of the finger and locked in adjusted position by anut constructed and arranged in a novel manner and also accessible fromthe forward end of the feed finger.

Another object is to provide a grippingelement of novelconstructionwhich enables a maximum amount of the stock bar to beused in a screwmachine.

A further object is to provide a gripping element axially compressibleto vary the work-gripping pressure and having a shoulder spaced from theend of the element to receive the adjusting Iorce.

The invention struction of the gripping element which enables the workbar to be gripped outwardly beyond the shoulder to which the axialpressure is applied.

' Other objects and advantages of the inveni tion will become apparentfrom the following detailed description taken in connection with theaccompanying drawings, in which Figure 1 is a longitudinal sectionalview of a feed finger embodying the novel features of the presentinvention, the finger being carried. in a screw machine mounting.

Fig. 2 is a longitudinal section taken along the line 2-2 of Fig. 1 ofone form of the work gripping element. 7

Fig. 3 is a section taken along the line 3-3 of Fig. 1. Fig. 4 is afragmentary exploded view of the head end of the feed finger. h

also resides in the novel con- 3 Fig. 5 is an elevational view ofanother form of the gripping element.

Fig. 6 is a perspective view of the gripping element shown in Fig. 2.

Figs. '1 and 8 are fragmentary longitudinal sectional views showingother modifications of the gripping element.

Fig. 9 is a fragmentary longitudinal sectional view showing the feedfinger in relation to the collet of an automatic screw machine.

While the invention is susceptible of various modifications andalternative constructions, I have shown in the drawings and will hereindescribe in detail the preferred embodiment. It is to be understood,however, that I do not intend to limit the invention by such disclosure,but aim to cover all modifications and alternative constructions fallingWithin the spirit and scope of the invention as expressed in theappended claims.

The invention is embodied for purposes of illustration in a feed fingerof the type in which a work bar H] is gripped by the internal surface llof a tubular sleeve l2 of yieldable material such as oil resistantrubber, the sleeve being disposed within a shell I3 mountable on thereciprocable feed tube or head [4 of an automatic screw machine. Theshell l3 comprises a steel tube formed at one end with an external screwthread I5 adapted to mate with the threaded bore in the screw machinehead M from which the feed fin.- ger projects in the direction of thestep-by-step advance oflthe work bar In toward the collet (not shown).

The shell has a generally cylindrical internal surface l6 terminating atone end in a shoulder ll which constitutes an abutment for one end ofthe work-gripping element l8. The latter com prises the yieldable sleevel2 and metallic end caps l9 and 20 therefor in the form of cups havingbottom holes 2| and 22 substantially equal in slze and cross-sectionalshape tothe bore H in the sleeve l2. The sleeve bore is somewhat largerthan the work bar I0 with which the gripping element is to be used, sothat by compressing the tube axially while radially confined by theshell I3, the internal tube surface will be contracted radially to gripthe work bar with a force proportional to the degree of such compressionand d stributed substantially uniformly over the tube surface H.

While both of the end caps may be of the same construction as shown inFig. 5, one cap, I9 in this instance, may be made of simplifiedconstruction comprising a cylindrical collar having an inturned flange23 defining the hole 2I and abutting against one end of the rubber tubeI2. Preferably, the flange 23 is coned to form an inwardly tapering endsurface by which guiding of a new work bar I through the grippingelement is facilitated.

In accordance with the present invention, at least one of the end caps,in this instance the cap 20, is formed with a tubular or outer endportion 24 of a diameter somewhat smaller than the sleeve I 2 andterminating in a rigid substantially right angular shoulder 25 spacedfrom the outer end of the cap which end is formed by an inturned flange26, preferably coned inwardly and defining the hole 22. As shown, theshoulder is of a width about half the radial thickness of the sleeve I2and is preferably formed by an outturned flange 21 integral with thetubular portion 24. This flange forms a rigid abutment for the outerportion of the rubber sleeve I2 while the inner portion of the rubbersleeve abuts against the flange 26, as a result of which the sleeve l2will be compressed axially throughout its-length in response to a forceexerted on the shoulder 25 ina direction to contract the elementaxially.

The flange 2! may terminate at the outer surface of the rubber sleeve I2as shown in Fig. 7, or, if desired, a cylindrical extension 28 (Figs. 1,2, and 6) integral with the flange 21 and flush with the outer sleevesurface may be extended a short distance along the sleeve. The caps I9and 20, which are preferably made of relatively "thin metal of uniformthickness, may be bonded tothe rubber of the sleeve during molding ofthe latter, or may be locked thereto mechanically -by providing holes 29either in the tubular portion 24 (Fig. 7) or in the extension 28 (Figs.1, -2, and 6). While the caps may be punched from sheet metal, they mayalso be turned from solid stock, in which case the rubber sleeve portionof reduced diameter would extend the full length of the cap 20 as shownin Fig. 8 and its extension 28 instead of only to the shoulder 25 as inthe forms shown in Figs. 2 and '7.

Preferably, the sleeve I2 is made of oil resistant or synthetic rubberor material having equivalent yielding properties, and is molded in oneintegral piece into the caps I9 and 20 to form a unitary assembly (Fig.6) of uniform internal size and cross section throughout its length, thesleeve I2 having a cylindrical external surface flush with the outersurfaces of the caps, which outer surfaces are only slightly smallerthan the internal surface I6 of the shell I3. Thus, the radial spacebetween the internal or gripping surface II and the outer cap surfacesis filled solidly with the yieldable material. This body acts as afluid, and, when confined radially by the shell l3, responds to endwisecompression to vary the radially directed pressure by which the internalrubber surface II grips the work bar I0. In this instance, thegrippingsurf-ace is smooth and continuous, but itmay, if desired, bemade of any preferred contour or be defined by harder metal parts setinto the rubber whose primary function is that of providing a fluid-likemedium for converting the axially applied compressive.

force to a radially directed gripping pressure.

The force for compressing the gripping element axially is derived by theaction of a hollow screw plug 3| threaded into the forward or free endof the shell l3 and having a central hole somewhat larger than thesmaller portion 24 of the cap 20. In the final assembly, this cap end isusually spaced inwardly from the outer plu end which has cross slots 32formed therein to receive a cylindrical wrench or a crossbar by whichthe plug may be turned into the shell and thus advanced into abutmentwith the shoulder 25 on the gripping element I6. Further advance of theplug compresses the rubber axially, resulting in gripping of the worksurface with a force proportional to the degree of axial compression ofthe rubber.

This gripping force is distributed substantially uniformly throughoutthe full length of the rubber surface ll including the part thereofoutwardly beyondthe shoulder 25 and within the reduced diameter 24 ofthe cap 20. This is for the reason that part of the compressive forceexerted on the shoulder 25 is transmitted through the rigid cap 20 andapplied to the end of the tubular portion 30. Thus, I have takenadvantage of the fiowa-bility of the yieldable material to maintain suchuniform pressure in spite of the fact that the shoulder 25 engaged bythe screw is spaced inwardly from the end 26 of the gripping element. Asa result and for the reasons mentioned later, the finger will feed agreater length of the work bar ID in an automatic screw machine, theincrease in length bein equal to the spacing of the shoulder 25 from theforward end of the gripping element.

To lock the plug 3| securely in its adjusted position, the inventioncontemplates the use of a nut 33 coacting with the end of the shell I3to increase the frictional engagement between the threaded parts of theshell and plug without at the same time increasing the overall externaldiameter of the finger. The nut comprises a ring equipped with meanssuch as flat surfaces 34 to engage a tool such as a wrench by which thenut may be tightened. A minimum diameter of the nut is made possible inthe present instance by reducing the diameter of the outer projectingend of the plug 3] and turning the nut onto an external thread 35 onthis reduced portion.

In the present instance, the locking action of the nut is produced bycontracting theforward end of the shell I3 around the plug 3|. For thispurpose, the shell is split as indicated at 36 at annularly spacedpoints and thus rendered somewhat flexible. The extreme end of the shellis tapered as indicated at 31, and this conical surface mates with andfits into an internal surface 38 on the inner end of the nut. As the nutis advanced along the thread 35 into engagement with the conicalsurfaces 3'! between the splits 3B, the latter surfaces are cammedinwardly into gripping engagement with the plug thread, theregay holdingthe plug frictionally against loosen- Location of the plug and thefriction lock therefor at the forward end of the shell facilitatesadjustment of the gripping pressure on the work bar without removal ofthe feed finger from the screw machine. To effect such adjustment, thenut 33 is first backed off by means of a Wrench applied to the flats 34after which the plug- 3| may be turned by a suitable wrench fitted intothe slots 32 in the exposed end of the plug.

The wastage of material as the work bar becomes used up in a screwmachine is reduced to a'minimum by virtue of the shouldered constructionof the ripping element :whose'smalle'r end may be extendedcompressionadjusting the work after its farthest advance in which,

as shown in Fig. 9, the end flange 26 of the gripping element isdisposed very close to the rear end of the collet jaws 36. As a result,the rubber surface continues to grip the work and feed it forwardlyuntil substantially the full length of the bar-has been fed into the'collet jaws and the end 40 of the work bar has reached the flange 26.Very little of the work bar at its trailing end is wasted, and, ascompared to prior feed finger constructions, a substantial saving isthus efiected which is especially important in the case of expensivematerials.

This application is a continuation-in-part of my prior applicationSerial No. 768,964, filed August 16, 1947, and now abandoned.

I claim as my invention:

1. A feed finger comprising a tubular shell threaded at one end formounting in an automatic screw machine, a shoulder within said shellfacing toward the second end of the shell, the latter shell end beingthreaded internally, a hollow plug threaded into said second shell endand providing a second shoulder within the shell facing toward saidshoulder, an elongated tube of resiliently yieldable material disposedwithin said shell in abutment with said shoulders and compressibleaxially by adjustment of said plug to reduce the internal diameter ofthe tube, said tube having an outer end portion of reduced diameterprojecting outwardly through the internally threaded end portion of theshell, and a cup of smaller diameter than the interior of said plugfitting over the exterior of said reduced end portion and having aninturned flange abutting against the outer end of the reduced portion toprevent the axial flow of said material as an incident to compression ofthe larger diameter portion of the tube between said shoulders.

2. A gripping element for a feed finger comprising an elongated tube ofresiliently yieldable material of generally cylindrical external contourthroughout the major portion of its length and of reduced diameter andcylindrical external contour over the remaining minor portion of itlength whereby to provide an axially facing shoulder at the junction ofthe larger and reduced end portions of the tube, a rigid ring on theouter end of the larger portion of the tube forming an abutment forapplying an endwise compressive force to the tube, a rigid cylindricalcup of an external diameter smaller than said larger tube portionsurrounding said reduced portion and confining the material thereofagainst outward flow, said cup having a flange at its outer end turnedinwardly at'the end of said tube and forming an abutment thereforpreventing endwise flow of said material, and an external rigid flangeon the inner end of said cup forming an abutment at the second end ofthe larger cylindrical portion of the tube.

3. A gripping element for a feed finger comprising an elongated tube ofresiliently yieldable material of generally cylindrical external contourthroughout the major portion of its length and of reduced diameter andcylindrical external contour over the remaining minor portion of itslength whereby to provide an axially facing shoulder at the'jun'ction ofthe larger and reduced end portions of the tube, and a rigid cylindricalcup of an external diameter smaller than said larger tube portionsurrounding said reduced portion, and having a flange at its outer endturned inwardly at the end of said tube and forming an abutment thereforpreventing endwise flow of the material.

'4. A grippingelement for a feed finger comprising an elongated tube ofresiliently yieldable material, a minor portion of the tube length atone end thereof being of reduced external diameter whereby to provide anaxially facing shoulder at the junction of the larger and reduceddiameters, a rigid cup of an external diameter smaller than the largertube portion surrounding said reduced portion and having a flange at itsouter end turned inwardly at the end of said tube and forming anabutment therefor preventing endwise flow of the material, and anexternal flange on the inner end of said cup abutting against saidshoulder.

5. A feed finger comprising a tubular shell contoured at one end formounting in an automatic screw machine, an abutment within said shelladjacent said end and facing toward the second end of said shell, thelatter shell end being threaded internally, a hollow plug threaded intosaid second shell end, a sleeve of yieldable material within said shellengaging said abutment at its inner end, the outer end portion of saidsleeve being of reduced diameter and projecting axially at leastpartially through said plug, a rigid flange abutting against the outerend of said reduced portion, a shoulder surrounding said reduced endportion at the inner end thereof, and a member surrounding said reducedportion and rigidly connecting said flange and said shoulder.

6. A feed finger comprising a tubular shell contoured at one end formounting in an automatic screw machine, an abutment within said shelladjacent said end and facing toward the second end of said shell, thelatter shell end being threaded internallyya hollow plug threaded intosaid second shell end, a sleeve-like gripping element within'said shellengaging said abutment at one end and having an end portion of reduceddiameter at its other end terminating at a shoulder spaced from thelatter end and. engageable with said plug, said element having aninternal surface contractible radially by axial compression of theelement between said abutment and plug, and a member rigidly connectingthe inner end of said plug and the outer end of said reduced portion forcompressing such portion axially simultaneously with the compression ofthe remaining portion. of the element between said plug andsaidabutment.

'7. A feed finger comprising a tubular shell contoured at one end formounting in an automatic screw machine, an abutment within said shelladjacent said end and facing toward the second end of said shell, thelatter shell end being threaded internally, a sleeve-like grippingelement of yieldable material within said shell engaging said abutmentat one end and having a portion of reduced diameter at the other endprojecting through said threaded shell end and terminating at an axiallyfacing shoulder, a rigid member having outturned and inturned flangesrespectively abutting against said shoulder and the outer end of saidreduced portion, and a plug surrounding said reduced portion andoutturned flange.

8. A feed finger comprising a tubular shell contoured at one end formounting in an automatic screw machine, an abutment within said shelladjacent said end and facing toward the second end of said shell, thelatter shell end being threaded internally, a sleeve of yieldablematerial disposed within said shell with one end engaging said abutment,the other end portion of said sleeve being of reduced diameter andterminating at a shoulder intermediate the ends of the sleeve, a plugsurrounding said reduced portion and screwed into the threaded shellend,

and an inturned abutment rigid withsaicl plug and engageable with theouter end of said reduced portion when the inner end of the plug isengaging said shoulder.

FRANK L. GREEN.

REFERENCES CITED The following references are of record in the file ofthis patent:

UNITED STATES PATENTS Number Name Date 2,426,200 Green Aug. 2 19472,547,522 Eichelman Apr. 3, 1951

